1. Field of the Invention
The present invention relates to a fuel injection valve for injecting fuel into an internal combustion engine or the like.
2. Description of Related Art
A conventional fuel injection valve includes a needle (valve member), which is driven electromagnetically to inject fuel into an internal combustion engine or the like (JP 2006-17101A, which corresponds to U.S. Pat. No. 7,252,245, and JP 2005-171845 A).
FIG. 15 of the accompanying drawings shows a conventional fuel injection valve (an injector) 91. The valve 91 includes a housing 910, which defines a fuel passage 96 therein, a movable core 922, and a needle 940. The core 922 and the needle 940 are integral with each other and is reciprocable axially in the housing 910. The needle 940 is biased by a compression spring 926 to close the valve 91.
The fuel injection valve 91 further includes a stator 921 and a coil 951. When current is supplied to the coil 951, magnetic attractive force is developed between the stator 921 and the movable core 922. The attractive force moves the core 922 and the needle 940 toward the stator 921 against the force of the compression spring 926 to open the valve 91. When the current supply to the coil 951 is cut off or the coil 951 is deenergized, the force of the spring 926 moves the core 922 and the needle 940 away from the stator 921 to close the valve 91.
When the coil 951 is supplied with current or is energized, the movable core 922, which is integral with the needle 940, collides with the stator 921 and bounces off the stator 921. As a result, particularly if the fuel injection valve 91 is driven for a short period of time, the injection quantity is not proportional to the time period, so that the quantity is difficult to control. As a result, it is impossible to reduce the minimum controllable injection quantity disadvantageously.
In order to solve this problem, a fuel injection valve is proposed, in which the movable core and the stator have a large contact area between them. As a result, the large contact area enlarges squeezing force developed between the movable core and the stator, and thereby a small bounce occurs when the coil of the fuel injection valve is supplied with current in the event of opening the valve. However, the large squeezing force makes the needle of the fuel injection valve less responsive in the event of closing the valve. This disadvantageously increases the minimum controllable injection quantity or causes another disadvantage associated with the injection characteristic of the fuel injection valve.